Adjustable induction coil for heating semiconductor rods

ABSTRACT

An adjustable induction coil is made up of several component parts, some of which may be disassembled from the remainder in order effectively to enlarge the inner diameter of the coil, or to remove the coil from association with a semiconductor rod passing through the coil, and which is heated by the coil. The coil is provided with conduits adapted to support a fluid flow for cooling the coil during operation.

0 I Unite States atent 1191 1111 3,827,017 Keller July 30, 1974 [54]ADJUSTABLE'INDUCTION COIL FOR 2,419,116 4/1947 Cassen et a1 219/1079HEATING SEMICONDUCTOR O S 2,456,091 12/1948 Stevens et a1 219/10792,459,971 1/1949 Stanton 336/62 X Inventor: g g Keller, m 2,481,0089/1949 Gagliardi et al. 219/1019 Germany 2,709,741 5/1955 Albrecht336/62 X 1 1 Assignee: Siemens Akflengesellscham Berlin 311531323 1/1323K223131512? 517131;. 3575/1535? and Munich, Germany 3,534,198 10/1970M11101 336/62 x N 24, 3,593,242 7/l97l AHClHSSOfl 336/62 [2]] AppL NOJ309,420 FOREIGN PATENTS OR APPLICATIONS 1,002,388 8/1965 Great Britain336/62 [30] Foreign Application Priority Data Examiner Thomas Kozma Dec.7, 1971 Germany 2160694 Atto y, Agent, or Firm-Hill, Gross, Simpson, Van

Santen, Steadman, Chiara & Simpson [52] US. Cl 336/62, 219/1079,336/223,

336/232 57 ABSTRACT [51] Int. Cl. 1101f 27/28 A bl d d f l [58] Field ofSearch 336/62, 232, 223; n a Justa e m ma 6 O Vera component parts, someof whlch may be d1sassemb1ed 219/1079 from the remamder 1n ordereffechvely to enlarge the 1561 1223331213211;1:21:31,sass/1211151231121UNITED STATES PATENTS the coil, and which is heated by the coil. Thecoil is 1,335,895 4/l920 Hughes 336/62 X provided onduits adapted toupport a flow 2,264,301 12 1941 Dcnnccn ct a1 219/1019 x for cooling theCO during Operation. 2,266,176 12/1941 Dcnnccn ct a1 219/1079 X2,404,987 7/1946 Rudd 219/1079 X 2 Claims, 7 Drawing Figures PATENTED I3,827,017

SHEET 1 [IF 3 ADJUSTABLE INDUCTION COIL FOR HEATING SEMICONDUCTOR RODSBACKGROUND OF THE INVENTION 1. Field of the Invention The presentinvention relates to induction coils and more particularly to inductioncoils which are employed in the process of treating semiconductor rodsby the floating zone melting process.

2. The Prior Art It is frequently desirable to purify rods consisting ofsemiconductor material by subjecting them to a socalled floating zonemelting process, employing an induction coil which heats thesemiconductor rod by in duction. A melting zone is established withinthe rod, which is encircled by the coil, and this melting zone isshifted along the length of the rod from one end to another, by movingthe rod relative to the coil. In this manner, impurities are transportedto one end of the rod, leaving the remaining structure more free ofimpurities than before. The floating zone melting process is also usedfor the breeding of single crystals by melting a core crystal to one endof the rod, and guiding a melting zone from the core crystal to theother end of the rod.

It is desirable to use a variety of sizes of induction coils in carryingout some heating processes, and it is therefore necessary sometimes toremove the coil from association with the rod, and to replace it withone of a different size. When a conventional coil construction isemployed, the coil can be removed only by disconnecting an end of thesemiconductor rod from the ap paratus which supports the rod during itsmovement relative to the coil. This is undesirable, especially whenrelatively large diameter rods such as 50 to 80 millimeters in diameter,are being treated. The disconnecting procedure is cumbersome andexpensive and it is desirable to avoid this procedure, if possible.

SUMMARY OF THE INVENTION A principal object of the present invention isto provide an induction heating coil which is constructed in a way whichpermits it to be dismounted from a semiconductor rod which it is adaptedto heat.

Another object of the present invention is to provide a coil which hasmeans for adjusting its inner diameter without removing it from asemiconductor rod which it is adapted to heat.

These and other objects and advantages of the pres ent invention willbecome manifest upon an inspection of the following description and theaccompanying drawings.

In one embodiment of the present invention there is provided a coilhaving two components which are selectively connectable with each otherand which are adapted to be separated from each other to permit removalof the coil from the semiconductor rod.

In another embodiment the coil consists of one or more loops with a ringshaped inner part formed of two components adapted to be separated fromeach other and from the coil loops.

BRIEF DESCRIPTION OF THE DRAWINGS Reference will now be made to theaccompanying drawings in which:

FIG. 1 is a perspective view of a coil incorporating an illustrativeembodiment of the present invention, shown in separated condition;

FIG. 2 is a plan view of the coil of F IG. 1, shown in assembledcondition;

FIG. 3 is a perspective view of an alternative embodiment of the presentinvention;

FIG. 4 is a plan view of a further embodiment of the present invention;

FIG. 5 is a vertical cross-sectional view of the coil of FIG. 4, takenalong a plane V-V;

FIG. 6 is a plan view of yet another embodiment of the presentinvention; and

FIG. 7 is a vertical cross-sectional view of the coil of FIG. 6, takenalong a plane VII-VII.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings,and in particular to FIGS. 1 and 2, a coil 1 is shown which is adaptedto be used for heating a semiconductor rod and which is selectivelyseparable from the rod. The coil 1 consists of a single loop, and isprovided with a pair of hollow conductive terminals 34 and 35, which maybe connected to a suitable source of electric potential to establish anelectric current within the coil. The terminals 34 and 35 are alsoconnected to a source of cooling fluid and to a sink therefor,respectively. The coil 1 is composed of copper or silver or some othermetal with good conducting properties. It is formed of two componentsections 2 and 3, which are in electrical contact with each other alongthe end surfaces thereof 4 and S.

The two sections 2 and 3 each have an interior conduit 31 connected atone end to the interior of the ho]- low terminals 34 and 35, and at theother end to each other via a sealing arrangement which prevents leakageof the fluid at the joint between the sections 2 and 3. A flange 32 isprovided on each of the sections 2 and 3 and each flange 32 havingaligned bolt holes 6, 7 and 8 by which the flanges 32 may be boltedtogether by bolts 6a and 7a. An O-ring 9 surrounds the joint between theconduits 31 to insure a fluid-tight sealing relationship between the twoflanges 32 when the same are bolted together. The surfaces of the twoflanges 32 are spaced slightly from the planes of the surfaces 4 and 5,to accomodate the thickness of the O-ring 9, permitting good electricalconnection between the surfaces 4 and 5. In one coil, the inner diameteris about 30 millimeters and the outer diameter is between millimetersand millimeters. Of course the sizes of the coil diameters depend on therod sizes which are to be used with the coil. When it is desired toremove the coil 1 from the rod with which it is associated, it may bereadily separated into two parts by disconnecting the nuts and boltsassociated with the bolt holes 6, 7 and 8, after which the two sections2 and 3 may be withdrawn separately from the semiconductor rod. Ofcourse, the fluid flow is stopped prior to disconnection to avoidspillage.

In FIG. 3, an alternative embodiment is illustrated which is like theembodiment shown in FIGS. 1 and 2 except that the separating linebetween the two sections 2 and 3 lies partly in the plane of the coil,rather than being transverse thereto as in the embodiment of FIGS. 1 and2. In other words, the separating line extends through the coil and isdefined by two parallel planes which extend perpendicular to the planeof the coil joined to a third plane between and perpendicular to theparallel planes. The two sections 2 and 3 are connected for goodelectrical contact therebetween, and with a fluid-tight seal, by meansof screws 6b and 7b. The screws 6b and 7b are received in alignedapertures in the two sections 2 and 3, those in the section 3 havingcooperating threads. The screws 6b and 7b are located on opposite sidesof junction between the interior conduits of the two sections. Theinterior conduit in each section is formed so that the junction betweenthe sections 2 and 3 is disposed solely on the horizontal surface 10, inthe manner shown in FIG. 7, which is described hereinafter. This insuresthat a fluid-tight seal is achieved by surrounding the opening on oneside or the other with a gasket member such as an O-ring.

The embodiment of FIG. 3 is preferable to that illustrated in FIGS. 1and 2 in some circumstances, when the screws 6b and 7b, being orienteddifferently from the bolts 6a and 7a, are more accessible.

In FIGS. 4 and 5 an alternative embodiment of the present invention isillustrated, showing an induction heating coil or loop 11 composed ofcopper, silver or the like having three convolutions 12 connectedbetween the hollow terminals 34 and 35. The coil 11 is formed of tubularmaterial to support a stream of cooling fluid. The winding includes twoarcuate inner sections 13 and 14 which are in electrical contact withthe inner convolution of the coil 11. A flange 30 is attached by meansof soldering, welding or the like, to the inner convolution 12 of thecoil 11, and the sections 13 and 14 are connected to the flange 30 bymeans of screws -22. As illustrated in FIG. 5, a solder joint 24 fillsthe space between the flange 30 and the inner convolution of the coil. Agap is provided in the flange 30 between the beginning and end of theinner convolution 12, to avoid short circuiting the convolution. A gapis also provided between the sections 13 and 14 at this location for thesame purpose.

When the screws 15-22 are removed, the two inner sections 13 and 14 areseparated and removed, thereby increasing the inner diameter of the coil11 from that illustrated in FIG. 4 to that illustrated in the dashedline 23, which defines the inner surface of the flange 30. The coilillustrated in FIGS. 4 and 5 may, therefore, be

employed in a process which requires coils of different inner diametersduring the course of the process. Of course it can also be used in aprocess involving a single semiconductor rod which is mounted in a waywhich permits the coil 11 to be removed therefrom only when its innerdiameter is as large as the dashed line 23.

In FIGS. 6 and 7 another embodiment of the present invention isillustrated. This embodiment resembles that shown in FIGS. 5 and 6except that the inner sections 13 and 14 are provided with an interiorconduit for cooling purposes. The coil 11 has two convolutions 12, andthe flange 30 is soldered by a solder joint 24 to the inner convolutionof the coil, just as in the embodiment of FIGS. 4 and 5. As bestillustrated in FIG. 7, the flange 30 has a rectangular cross-section,and includes a horizontal bore 36 communicating at one end with theinterior of the inner convolution 12 of the coil 11, and at the otherend with a vertical bore aligned with a vertical bore 37 provided in thesections 13 and 14 and leading to the hollow interior of the sections 13and 14. By this means the inner convolution is connected to the innersections at four locations, and cooling fluid flows through the hollowinner sections 13 and 14, as well as through the coil 11, as illustratedby the arrows 25. Both of the sections 13 and 14 have end walls closingoff the ends of the conduit therewithin, so no sealing arrangement isneeded at the vertical plane of contact between the sections 13 and 14.Four O-rings 26-29 surround the four fluid junction points between thetwo inner sections 13 and 14 and the ring flange 30, as best illustratedin FIG. 6, to insure a fluid-tight connection therebetween. Screws 15-22interconnect the inner sections 13 and 14 to the ring flange 30 in thesame manner as has been described in reference to FIGS. 4 and 5.

The embodiment shown in FIGS. 6 and 7 may be employed in the same manneras that illustrated in FIGS. 4 and 5, but the embodiment of FIGS. 6 and7 achieves the additional advantage of permitting cooling of the innersections 13 and 14.

What is claimed is:

1. An induction heating coil for use in heating a semiconductor rodcomprising:

an induction coil adapted to encircle said rod and including a currentconducting loop forming an outer section of said coil and a plurality ofseparable inner sections, whereby at least some of said inner sectionsmay be independently separated from association with said rod;

said loop formed of a plurality of convolutions of an elongated tube;

said inner sections being removably connected with an innermostconvolution of said loop, said inner sections being in substantiallycontinuous electrical contact with said innermost convolution of saidloop, said inner sections having a radially innermost surface defining acircle for surrounding said rod, said inner sections being separablefrom each other along a separating line;

an insulating space separating one end of said innermost convolutionfrom the other end of said innermost convolution;

conduit means within said inner sections for supporting a fluid flowtherethrough; and

means for connecting the interior of the tube of said innermostconvolution with said conduit means.

2. A disassembleable induction heating arrangement for floating zonemelting of semiconductor rods comprising:

a flat coil having at least two separable components contacting eachother along a separating line; means for securing said componentstogether; a fluid passageway through each of said components; and gasketmeans for forming a fluid-tight connection therebetween; said separatingline extending through said coil and being defined by two parallelplanes which extend perpendicular to the plane of said coil joined to athird plane between and perpendicular to said parallel planes.

1. An induction heating coil for use in heating a semiconductor rodcomprising: an induction coil adapted to encircle said rod and includinga current conducting loop forming an outer section of said coil and aplurality of separable inner sections, whereby at least some of saidinner sections may be independently separated from association with saidrod; said loop formed of a plurality of convolutions of an elongatedtube; said inner sections being removably connected with an innermostconvolution of said loop, said inner sections being in substantiallycontinuous electrical contact with said innermost convolution of saidloop, said inner sections having a radially innermost surface defining acircle for surrounding said rod, said inner sections being separablefrom each other along a separating line; an insulating space separatingone end of said innermost convolution from the other end of saidinnermost convolution; conduit means within said inner sections forsupporting a fluid flow therethrough; and means for connecting theinterior of the tube of said innermost convolution with said conduitmeans.
 2. A disassembleable induction heating arrangement for floatingzone melting of semiconductor rods comprising: a flat coil having atleast two separable components contacting each other along a separatingline; means for securing said components together; a fluid passagewaythrough each of said components; and gasket means for forming afluid-tight connection therebetween; said separating line extendingthrough said coil and being defined by two parallel planes which extendperpendicular to the plane of said coil joined to a third plane betweenand perpendicular to said parallel planes.